Method for controlling a compressor of a thermal storage heat pump system

ABSTRACT

A method of controlling a compressor of a thermal storage heat pump system of a vehicle is provided. The system may operate in one of a heating mode and a cooling mode, as determined by at least one system controller based on at least one parameter. The at least one parameter may be ambient air temperature. The compressor has a compressor motor and a motor controller configured to selectively operate the compressor in an unmodified state or a modified state based on the operating mode of the system. The compressor motor is operated in the unmodified state when the system is in the cooling mode, and in the modified state when the system is in the heating mode. Operating the compressor motor in the modified state may include decreasing its coefficient of performance (COP).

TECHNICAL FIELD

The present invention relates to a method for controlling a compressor of a thermal storage heat pump system in a vehicle, such as a hybrid electric vehicle (HEV) or a plug-in hybrid electric vehicle (PHEV).

BACKGROUND

An electric vehicle, such as a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or the like, generally includes an electric motor, which may alone propel the vehicle in an electric vehicle (EV), or charge-depleting, drive mode. The vehicle may also include an internal combustion engine (ICE) to serve as the primary propulsion system of the vehicle in a range extending mode, or to operate in conjunction with the electric motor in a hybrid, or charge-sustaining, mode.

The electric motor generally receives electric power from an electric power source, such as an energy storage system (ESS). The ESS may include a battery pack or other rechargeable energy storage means capable of storing large amounts of thermal energy. The ESS may store the thermal energy when the vehicle is connected to an external power source, such as an electrical grid, for charging. In colder ambient temperatures, the charge depletes faster, due to various factors.

The ESS may be used in conjunction with a thermal management system, such as a heat pump system, thereby forming a thermal storage heat pump system, to transfer the stored thermal energy to another medium for another purpose, such as to heat a passenger compartment of the vehicle.

The heat pump system (and therefore, the thermal storage heat pump system) generally includes a compressor, which compresses refrigerant serving as the heat transfer medium for the heat pump system. The compressor motor requires a certain amount of electric power, which in turn is converted to electric heat, to function in compressing the refrigerant. The electric power necessary is dependent upon the coefficient of performance (COP) of the compressor motor. As the COP increases, the compressor motor requires less electric power.

SUMMARY

A thermal storage heat pump system of a vehicle having a passenger compartment is provided. The thermal storage heat pump system generally includes a first coolant circuit, a second coolant circuit, and a refrigeration circuit that are configured to circulate a first coolant, a second coolant, and a refrigerant, respectively. The refrigeration circuit is in thermal communication with the first coolant circuit and the second coolant circuit via a first heat exchanger and a second heat exchanger, respectively.

The thermal storage heat pump system also includes a compressor located in the refrigeration circuit. The compressor is configured to compress the refrigerant in the refrigeration circuit. The compressor has a compressor motor and a motor controller configured to selectively operate the compressor motor in one of an unmodified state and a modified state. The compressor motor may be a brushless direct current (DC) electric motor that has a coefficient of performance (COP), and is a three-phase electric system in which each phase is offset by a set angle and has a defined frequency in the unmodified state. In the modified state, the COP is less than that in the unmodified state.

The thermal storage heat pump system further includes at least one system controller configured to selectively operate the thermal storage heat pump system in one of a heating mode and a cooling mode based on at least one parameter. The at least one parameter may be ambient air temperature. When the ambient air temperature is at or below a switchover temperature, the thermal storage heat pump system may operate in the heating mode. When the ambient air temperature is above the switchover temperature, the thermal storage heat pump system may operate in the cooling mode. The compressor motor is operated in the unmodified state when the thermal storage heat pump system is in the cooling mode, and in the modified state when the thermal storage heat pump system is in the heating mode.

A method for controlling the compressor of the thermal storage heat pump system described above is also provided. The method includes first receiving, by the at least one system controller, a measurement of at least one parameter. As explained above, the at least one parameter may be ambient air temperature. The method then includes determining, by the at least one system controller, the operating mode of the thermal storage heat pump system based on the measurement.

The method then includes operating, by the motor controller, the compressor motor in one of the unmodified state and the modified state. Again, the compressor motor is operated in the unmodified state when the thermal storage heat pump system is in the cooling mode, and in the modified state when the thermal storage heat pump system is in the heating mode.

Operating the compressor motor in the modified state may include reducing the COP of the compressor motor. This may further include offsetting from the set angle at least one of the three phases and/or altering the defined frequency of at least one of the three phases.

The above features and advantages, and other features and advantages, of the present invention are readily apparent from the following detailed description of some of the best modes and other embodiments for carrying out the invention, which is defined solely by the appended claims, when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a thermal storage heat pump system having a compressor with a compressor motor;

FIG. 2 is a schematic diagram of the compressor motor of FIG. 1;

FIG. 3 is a schematic, flow diagram of a method for controlling the compressor;

FIG. 4 is a schematic flow diagram illustrating one step of the method of FIG. 3;

FIG. 5 is a graph illustrating a relationship between the coefficient of performance (COP) of the compressor motor and the ambient air temperature; and

FIG. 6 is a graph illustrating a relationship between electrical heat produced by the compressor motor and the ambient air temperature.

DETAILED DESCRIPTION

The following description and figures refer to example embodiments and are merely illustrative in nature and not intended to limit the invention, its application, or uses. Throughout the figures, some components are illustrated with standardized or basic symbols. These symbols are representative and illustrative only, and are in no way limiting to any specific configuration shown, to combinations between the different configurations shown, or to the claims. All descriptions of componentry are open-ended and any examples of components are non-exhaustive.

Referring to the drawings, wherein like reference numbers correspond to like or similar components wherever possible throughout the several figures, a thermal storage heat pump system 100 for use in a vehicle 101, including, but not limited to, a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or the like, is shown in FIG. 1. The vehicle 101 may selectively operate in a range extending mode, a hybrid, or charge-sustaining, mode, and an electric vehicle (EV), or charge-depleting, drive mode. In range extending mode, an internal combustion engine (ICE) 128, described hereinafter, operates as the sole propulsion system for the vehicle 101. In hybrid mode, the vehicle 101 operates using both electric power from an electric motor (not shown) and power from the ICE 128. In EV drive mode, the vehicle 101 operates solely on electricity.

The thermal storage heat pump system 100 generally includes a refrigeration circuit 103 in thermal communication with a first coolant circuit 104 and a second coolant circuit 105 via a first heat exchanger 106 and a second heat exchanger 107, respectively. The refrigeration circuit 103, the first coolant circuit 104, and the second coolant circuit 105 are configured to circulate a refrigerant, a first coolant, and a second coolant, respectively. The first heat exchanger 106 may be a refrigerant-to-liquid chiller heat exchanger that may function as a heat pump evaporator to dissipate heat from the first coolant in the first coolant circuit 104 to the refrigerant in the refrigeration circuit 103. The second heat exchanger 107 may also be a refrigerant-to-liquid heat exchanger that may function as a heat pump condenser to dissipate heat from the refrigerant in the refrigeration circuit 103 to the second coolant in the second coolant circuit 105.

The refrigeration circuit 103 includes a compressor 108 located downstream of the first heat exchanger 106 and upstream of the second heat exchanger 107. The compressor 108 may be configured to compress the refrigerant. The compressor 108 is driven by a compressor motor 109, which may be a brushless direct current (DC) electric motor, as depicted in the schematic diagram in FIG. 2.

Referring now to FIG. 2, the compressor motor 109 generally receives a DC power input signal from a power source 110. An inverter 111 converts the DC signal into an alternating current (AC) signal to drive the compressor motor 109. The compressor motor 109 generally is a three-phase system, and as such, has three motor windings 112 around a rotor 113 to receive the AC signal. While the motor windings 112 are shown in a wye (Y) configuration, it should be appreciated that they may be in a delta (Δ) configuration as well. In an unmodified state of the compressor motor 109, in which the compressor motor 109 is most efficient, each phase is offset by a set angle equivalent to one third of a period, or 120 degrees. In addition, each phase runs at a defined frequency. As explained in method 200 hereinafter, these and other characteristics of the compressor motor 109 may be modified to reduce its coefficient of performance (COP), i.e., make it less efficient.

The compressor motor 109 further includes a motor controller 114 configured to control the operation of the compressor motor 109, including, but not limited to, the speed and position of the rotor 113 of the compressor motor 109, the frequency and offset of the three phases, commutation, and the like.

Referring back to FIG. 1, the refrigeration circuit 103 also includes a first thermal expansion device 115, a second thermal expansion device 116, and a third heat exchanger 117. The third heat exchanger 117 may be an ambient-to-refrigerant heat exchanger that may function as a cabin evaporator. It may be configured to absorb heat from the air flowing across it to cool and dehumidify the passenger compartment 102, and to transfer the heat to the refrigerant flowing through it. The refrigerant may then be distributed to the compressor 108 and subsequently to the second heat exchanger 107, where the heat in the refrigerant may be absorbed by the second coolant, as explained above.

The first thermal expansion device 115 and the second thermal expansion device 116 may be located downstream of the second heat exchanger 107, and may be configured to cool and expand the refrigerant to be distributed to the first heat exchanger 106 and to the third heat exchanger 117, respectively. The first thermal expansion device 115 and the second thermal expansion device 116 may be thermostatic or thermal expansion valves, and may be either electronically or mechanically actuated.

The refrigeration circuit 103 may also include a fourth heat exchanger 118. The fourth heat exchanger 118 may be a refrigerant-to-ambient heat exchanger, and may function as a condenser for an air conditioning (A/C) system (not shown) in the vehicle 101.

The refrigeration circuit 103 may further include a plurality of flow control valves 119, 120, 121, and 122. The flow control valves 119, 120, 121, and 122 may be configured to control the flow to the various components in the refrigeration circuit 103. It should be appreciated that the flow control valves 119, 120, 121, and 122 may be any valve capable of restricting the flow of refrigerant in a particular line, and may be, but are not limited to, two-position, open/closed valves, or alternatively, modulating valves.

The first coolant circuit 104 includes a thermal storage device 123 and a first coolant pump 124. The thermal storage device 123 may be any medium, device, machine, or the like, capable of generating and storing thermal energy. For example, the thermal storage device 123 may be an energy storage system (ESS) that includes at least one battery or battery pack.

The first coolant pump 124, which may be variable speed, may be configured to circulate the first coolant through the thermal storage device 123 such that the first coolant may absorb heat generated by the thermal storage device 123, or deposit heat within the thermal storage device 123. The first coolant pump 124 further may be configured to circulate the first coolant through the first heat exchanger 106 such that heat may be transferred from the first coolant to the refrigerant, as explained above. While the first coolant pump 124 is shown downstream of the thermal storage device 123, it should be appreciated that it may be located upstream of the thermal storage device 123.

The first coolant circuit 104 also may include a heater 125. The heater 125 may be configured to heat the first coolant in the first coolant circuit 104, which flows to the thermal storage device 123 where the heat may be deposited and stored. The heater 125 may be, but is not limited to, a resistive heater.

The second coolant circuit 105 includes a heater core 126 and a second coolant pump 127. The second coolant pump 127, which may be variable speed, may be configured to circulate the second coolant through the heater core 126. The heater core 126, in turn, may be configured to receive the second coolant to heat air flowing across it and into the passenger compartment 102. As explained above, the second coolant may receive heat from the thermal storage device 123 via the first heat exchanger 106, and/or from the ambient air via the third heat exchanger 117. While the second coolant pump 127 is shown downstream of the heater core 126, it should be appreciated that it may be located upstream of the heater core 126.

The second coolant circuit 105 also may include the ICE 128, mentioned above. The ICE 128 may have heat within it from having been in operation. The heat may be deposited in the second coolant as it flows through the ICE 128, thereby cooling the ICE 128.

The second coolant circuit 105 further may include a bypass valve 129 and a bypass line 130. The bypass valve 129 is configured to selectively direct the second coolant to the ICE 128 to cool it when the vehicle 101 is in range extending mode or hybrid mode, or to the bypass line 130 when the vehicle 101 is in EV drive mode. While the bypass valve 129 is shown in FIG. 1 as a two-position three-way valve, it should be appreciated that the bypass valve 129 may be any three-way valve configured to selectively direct the flow to the ICE 128 and/or to the bypass line 129. In an alternative embodiment not shown, in lieu of a three-way valve, there may be two separate flow control valves, one each on the bypass line 130 and the second coolant circuit 105 downstream of the takeoff for the bypass line 130.

The thermal storage heat pump system 100 may also include at least one system controller 131 that may be electrically connected to the thermal storage heat pump system 100 to control its operation. In particular, the system controller 131 may communicate with and control the operation of various devices of the thermal storage heat pump system 100, including the motor controller 114, based on at least one parameter, including, but not limited to, ambient air temperature, as described in method 200 hereinafter.

The system controller 131 also may be configured to communicate with and receive information from other ancillary devices, including, but not limited to, a temperature sensor 132 and an input module 133, describer hereinafter. The system controller 131 may process the information received from these ancillary devices to determine the operating mode in which the thermal storage heat pump system 100 is to operate, and to operate the devices accordingly. As explained hereinafter, the thermal storage heat pump system 100 may operate in a heating mode or in a cooling mode. The system controller 131 may further be configured to control any other devices in the thermal storage heat pump system 100, as well as any other subsystems in the vehicle 101.

The temperature sensor 132 generally is any device configured to measure the ambient air temperature. The temperature sensor 132 may be configured to transmit data, such as the ambient air temperature measurement, to the system controller 131 to be stored and/or processed. The temperature sensor 132 may be external to the system controller 131, as depicted in FIG. 1, and may transmit the data through a wired or wireless connection. In another embodiment not shown, the temperature sensor may be internal to the system controller 131. In yet another embodiment not shown, the system controller 131 may be configured to obtain such data as the ambient air temperature from a remote source (not shown) via the internet or other communications network.

The input module 133 may be any device configured to receive an input, such as a desired temperature or heat supply for the passenger compartment 102, or other data from a user of the thermal storage heat pump system 100. The input module 133 further may be configured to transmit such data to the controller 131. The input module 133 may be, but is not limited to, an onboard computer in the vehicle 101.

As mentioned above, the thermal storage heat pump system 100 may operate in a heating mode or a cooling mode. In the heating mode, the refrigerant in the refrigeration circuit 103 may be used to transfer heat to the second coolant in the second coolant circuit 105 via the second heat exchanger 107 to heat the passenger compartment 102 via the heater core 126, as explained above. Conversely, in the cooling mode, the refrigerant may be used to absorb heat from the ambient air via the third heat exchanger 117 to cool the passenger compartment 102. The thermal storage heat pump system 100 may selectively switch between the two modes based on a parameter, such as ambient air temperature.

In either mode, the refrigerant in the refrigeration circuit 103 is utilized to transfer heat, and as such, the compressor 108 and compressor motor 109 operate to compress the refrigerant. The compressor motor 109 requires a certain amount of electrical power received from the power source 110 to operate. In compressing the refrigerant, the compressor motor 109 converts the electrical power into electrical heat, which then may be transferred to the refrigerant.

In the heating mode, the electrical power necessary for the compressor motor 109, and thus the electrical heat produced by the compressor motor 109, is equal to the total thermal load required to heat the passenger compartment 102 divided by the COP of the compressor motor 109. The total thermal load required may be determined by the system controller 131 based on a desired temperature or heat supply for the passenger compartment 102 as received from the input module 133. The remaining thermal load not provided by the electrical heat produced from the compressor motor 109 may be provided from the thermal storage device 123.

Referring now to FIGS. 5 and 6, the effect of modifying the COP, represented by the y-axis 302 in FIG. 5, on the electrical heat produced, represented by the y-axis 312 in FIG. 6, when switching between the heating and cooling modes, represented by sections 308 and 310, respectively, in FIGS. 5 and 6, is shown. The x-axis 304 in FIGS. 5 and 6 represents the ambient air temperature. As explained above, the compressor motor 109 may be made less efficient by modifying its characteristics to reduce its COP. Generally, the compressor motor 109 is in its unmodified state in the cooling mode. However, by reducing the COP in the heating mode, the electrical heat produced increases with a fixed total thermal load required. As such, the amount of thermal load to be drawn from the thermal storage device 123 may decrease. This in turn may decrease the need to operate the heater 125 to provide the heat stored in the thermal storage device 123.

Referring now to FIG. 3, a method 200 for controlling the thermal storage heat pump system 100, particularly the compressor 108 and the compressor motor 109, is shown.

Method 200 begins at step 202 in which the system controller 131 receives a measurement of at least one parameter. The at least one parameter may be, but is not limited to, ambient air temperature. As explained above, the ambient air temperature measurement may be taken and transmitted to the system controller 131 by the temperature sensor 132.

After step 202, method 200 proceeds to step 204. At step 204, the system controller 131 determines the operating mode of the thermal storage heat pump system 100 based on the measurement of the at least one parameter. As explained above, the thermal storage heat pump system 100 may operate in either a heating mode or a cooling mode.

When the measurement of the at least one parameter meets a certain condition, the thermal storage heat pump system 100 will operate in the particular mode associated with that condition. For example, as seen in the graphs of FIGS. 5 and 6, when the ambient air temperature (x-axis 304) is at or below a switchover temperature 306, the thermal storage heat pump system 100 may operate in the heating mode (section 308). Conversely, when the ambient air temperature is above the switchover temperature 306, the thermal storage heat pump system 100 may operate in the cooling mode (section 310). The switchover temperature may be stored in the system controller 131, and may be adjustable.

After step 204, method 200 proceeds to step 206. At step 206, the compressor controller 114 operates the compressor motor 109 in either an unmodified state or a modified state, depending on the mode of operation. As explained above, when the thermal storage heat pump system is in the cooling mode, the compressor controller 114 operates the compressor motor 109 in the unmodified, or most efficient, state. When the thermal storage heat pump system 100 is in the heating mode, the compressor controller 114 operates the compressor motor 109 in the modified state in which its COP is decreased. This may include several sub-steps, as depicted in FIG. 4.

Referring to FIG. 4, at sub-step 206 a, the compressor controller 114 may offset from the set angle at least one of the three phases of the compressor motor 109. For example, the compressor controller 114 may offset one of the phases by 30 degrees. At sub-step 206 b, the compressor controller 114 may alter the defined frequency of at least one of the three phases. As explained above, each phase operates at a defined frequency. Altering at least one of them may reduce the COP. It should be appreciated that step 204 may include any one of sub-steps 206 a and 206 b, which may be performed in any order. It should further be appreciated that step 206 may include more sub-steps in which the compressor motor 109 may be altered in other ways, such as internal motor restriction, mechanical losses internal to the compressor motor 109 (or frictional losses), mechanical braking, and the like, to reduce the COP.

The detailed description and the drawings or figures are supportive and descriptive of the invention, but the scope of the invention is defined solely by the claims. While some of the best modes and other embodiments for carrying out the claimed invention have been described in detail, various alternative designs and embodiments exist for practicing the invention defined in the appended claims. 

1. A method for controlling a compressor of a thermal storage heat pump system in a vehicle having a passenger compartment, the thermal storage heat pump system including a refrigeration circuit in thermal communication with a first coolant circuit and a second coolant circuit, the compressor being located in the refrigeration circuit and having a compressor motor and a motor controller, the method comprising: receiving, by at least one system controller, a measurement of at least one parameter; determining, by the at least one system controller, an operating mode of the thermal storage heat pump system based on the measurement of the at least one parameter; and operating, by the motor controller, the compressor motor in one of an unmodified state and a modified state based on the operating mode of the thermal storage heat pump system; wherein the operating mode is one of a heating mode and a cooling mode; and wherein the compressor motor is operated in the unmodified state when the thermal storage heat pump system is in the cooling mode, and in the modified state when the thermal storage heat pump system is in the heating mode.
 2. The method of claim 1 wherein the at least one parameter is ambient air temperature.
 3. The method of claim 2 wherein the measurement of the ambient air temperature is taken and transmitted to the at least one system controller by a temperature sensor.
 4. The method of claim 2 wherein the operating mode is the heating mode when the measurement of the ambient air temperature is at or below a switchover temperature, and is the cooling mode when the measurement of the ambient air temperature is above the switchover temperature.
 5. The method of claim 1 wherein the compressor motor is a brushless direct current (DC) electric motor that has a coefficient of performance (COP), and is a three-phase system in which each phase is offset by a set angle and has a defined frequency in the unmodified state.
 6. The method of claim 5 wherein the operating of the compressor motor in a modified state comprises reducing the COP of the compressor motor.
 7. The method of claim 6 wherein the reducing of the COP comprises offsetting from the set angle at least one of the phases of the compressor motor.
 8. The method of claim 6 wherein the reducing of the COP comprises altering the defined frequency of at least one of the phases of the compressor motor.
 9. A thermal storage heat pump system of a vehicle having a passenger compartment, the system comprising: a first coolant circuit configured to circulate a first coolant; a second coolant circuit configured to circulate a second coolant; a refrigeration circuit configured to circulate a refrigerant, the refrigeration circuit being in thermal communication with the first coolant circuit and the second coolant circuit via a first heat exchanger and a second heat exchanger, respectively; a compressor located in the refrigeration circuit, the compressor being configured to compress the refrigerant, and having a compressor motor and a motor controller configured to selectively operate the compressor motor in one of an unmodified state and a modified state; and at least one system controller configured to selectively operate the thermal storage heat pump system in one of a heating mode and a cooling mode based on a measurement of at least one parameter; wherein the compressor motor is operated in the unmodified state when the thermal storage heat pump system is in the cooling mode, and in the modified state when the thermal storage heat pump system is in the heating mode.
 10. The thermal storage heat pump system of claim 9 wherein the at least one parameter is ambient air temperature.
 11. The thermal storage heat pump system of claim 10 further comprising a temperature sensor configured to measure the ambient air temperature to obtain an ambient air temperature measurement, and to transmit the ambient air temperature measurement to the at least one system controller.
 12. The thermal storage heat pump system of claim 11 wherein the operating mode is the heating mode when the ambient air temperature measurement is at or below a switchover temperature, and is the cooling mode when the ambient air temperature measurement is above the switchover temperature.
 13. The thermal storage heat pump system of claim 9 wherein the compressor motor is a brushless direct current (DC) electric motor that has a coefficient of performance (COP), and is a three-phase system in which each phase is offset by a set angle and has a defined frequency in the unmodified state.
 14. The thermal storage heat pump system of claim 13 wherein the COP when the thermal storage heat pump system is in the heating mode is less than the COP when the thermal storage heat pump system is in the cooling mode.
 15. The thermal storage heat pump system of claim 14 wherein at least one of the phases of the compressor motor is offset from the set angle.
 16. The thermal storage heat pump system of claim 14 wherein at least one of the phases has an altered frequency different from the defined frequency.
 17. A method for controlling a compressor of a thermal storage heat pump system having at least one system controller and a refrigeration circuit in which the compressor is located, the compressor having a compressor motor and a motor controller, the method comprising: measuring, by a temperature sensor, ambient air temperature to obtain a temperature measurement; transmitting, by the temperature sensor, the temperature measurement to the at least one system controller; determining, by the at least one system controller, an operating mode of the thermal storage heat pump system based on the temperature measurement, the operating mode being one of a heating mode and a cooling mode; and operating, by the motor controller, the compressor motor in an unmodified state when the thermal storage heat pump system is in the cooling mode, and in the modified state when the thermal storage heat pump system is in the heating mode.
 18. The method of claim 17 wherein the operating mode is the heating mode when the temperature measurement is at or below a switchover temperature, and is the cooling mode when the temperature measurement is above the switchover temperature.
 19. The method of claim 17 wherein the compressor motor is a brushless direct current (DC) electric motor that has a coefficient of performance (COP), and is a three-phase system in which each phase is offset by a set angle and has a defined frequency in the unmodified state.
 20. The method of claim 19 wherein the operating of the compressor motor in a modified state comprises reducing the COP of the compressor motor by at least one of offsetting from the set angle at least one of the phases of the compressor motor, altering the defined frequency of at least one of the phases of the compressor motor, and adding mechanical losses internal to the compressor motor. 